Patients diagnosed as having perforated diverticulitis with free air on plain abdominal X-ray or CT scan fulfilling the in- and exclusion criteria are randomised during laparoscopy via a central computer. In case of purulent diverticulitis patients are randomised to three arms: (a) laparoscopic lavage, (b) sigmoidectomy with colostomy or (c) sigmoidectomy with anastomosis in ratio of 2:1:1. In case of faecal peritonitis or an overt perforation of the sigmoid, the patient will be randomised 1:1 to sigmoidectomy with colostomy or sigmoidectomy with primary anastomosis.